1. Field of the Invention
This invention relates in general to the processing of acoustic signals and more particularly, to processing of acoustic signals in relation to signal suppression and the configuration of components based on the acoustic signals.
2. Description of the Related Art
The use of portable electronic devices has risen in recent years. Cellular telephones, in particular, have become very popular with the public. The primary purpose of cellular phones is for voice communication. Many cell phones are equipped with a high-audio speaker that allows a user to engage in a cell phone conversation with a caller at a handheld distance without having to hold the phone next to the user's ear. This process is commonly referred to as speakerphone mode. Generally, during this speakerphone mode, the volume level of the speaker output is increased and the microphone sensitivity is raised to increase the voice loudness of the caller. The amplification of the speaker output and increased gain sensitivity of the microphone, however, can cause a feedback condition. In particular, the speaker output that is played to the user can reverberate in the environment in which the phone resides and may feed back as an echo into the user microphone. The caller may hear this feedback as an echo of his or her voice, which can be annoying. For this reason, echo suppressors are routinely employed to remove the echo from the receiving handset to prevent the caller from hearing his or her own voice at the calling handset.
Echo suppressors, however, cannot completely remove the echo in Speakerphone mode because they have difficulty modeling the acoustic path due to mechanical and environmental non-linearities. Moreover, an echo suppressor can become confused when the user of the receiving unit talks at the same time the caller's voice is being played out the speakerphone. This scenario is commonly referred to as a double-talk condition, which produces an acoustic signal that includes the output audio from the speaker (speaker output) and the user's voice, both of which are captured by a microphone of the user's handset. The echo suppressor cannot completely attenuate the echo of the speaker output due to the voice activity of the double-talk condition.
Voice activity detectors (VADs) are routinely employed to determine when voice is present on a communication channel for facilitating the sending of voice. The VAD can save bandwidth since voice is transmitted only when voice is present. The VAD relies on a decision that determines whether voice is present or not. In a half-duplex system, the VAD may only allow one user to speak at a time. During the occurrence of double-talk, the voice activity in the speaker output may contend with the voice activity of the user. A user may want to break into the conversation while the caller is speaking, without having to wait for the caller to finish talking; this is termed near-end break-in. That is, the user wants to say something at that moment but may be unable because of the VAD's inability to detect near-end voice during the double-talk condition. The performance of the VAD is also highly dependent on the volume level of the output speech.